What is case law?

5 mins read

Case law is a key component of the legal system and if you’re considering a career in law you’ll need to familiarise yourself with it. Below we explore what case law is, how it can affect future judicial decisions and shape the law as we know it.

By Grant Longstaff. Published 3 April 2024. Updated 21 November 2025.

Why is case law important?

Simply put, case law is a law which is established following a decision made by a judge or judges. Case law is developed by interpreting and applying existing laws to a specific situation and clarifying them when necessary. This process then sets a legal precedent which other courts are required to follow, and it will help guide future rulings and interpretations of a particular law.

Case law plays a significant role in shaping the legal system and ensures it evolves when necessary. It can provide clarity and guidance to legal professionals on how laws are interpreted and applied in real life situations, and helps to ensure consistency in court rulings by drawing on the legal precedents which have informed previous cases.

How case law works

Case law develops through a process of judicial reasoning and decision making. The parties involved in a legal dispute will present their arguments and evidence in a court of law. The judge then considers all of the legal principles, statutes and precedents before reaching a decision. This decision – known as a judgement – becomes part of the body of case law.

Depending on your future practice area you may need to regularly find and interpret case law to establish if it’s still suitable. Remember, case law evolves, and so a decision which once was solid may now be lacking.

This all may feel a little daunting right now, but if you choose to study law you’ll come to understand the importance of case law, develop keen research skills, explore legal case studies and learn of the judicial decisions which have shaped today’s justice system.

Judicial decisions and precedents

Judicial decisions are key to developing case law as each decision contributes to the body of legal precedents shaping future rulings. These precedents are binding and must be followed by lower courts. You can find a detailed guide to the court structure in the UK on the Courts and Tribunals Judiciary website.

When it comes to reviewing these judicial principles and legal precedents, you’ll likely find they come as either a law report or transcript. A transcript is simply a written record of the court’s judgement. A law report on the other hand is generally only written when the case sets a precedent. The Incorporated Council of Law Reporting for England and Wales (ICLR) – the official law reporting service – describes law reports as a “highly processed account of the case” and will “contain all of the components you’ll find in a transcript, along with a number of other important and useful elements of content.” It’s also worth remembering a law report will wield more weight than a transcript when it comes to building your legal case or argument.

Common law and stare decisis

Common law refers to the wider legal system which was developed in medieval England and has evolved throughout the centuries since. It relies deeply on case law, using the judicial decisions and precedents, to change over time. Case law helps establish new principles and redefine existing ones. It also helps resolve any ambiguity and allows for nuance to be incorporated into common law.

When it comes to case law you’ll likely come across the term “stare decisis”, a Latin phrase, meaning “to stand by decisions”. In a legal setting, stare decisis refers to the principle that decisions made by higher courts are binding on lower courts, promoting fairness and stability throughout common law and the legal system.

What are the key concepts of case law?

In case law you’ll encounter a number of phrases, such as precedents and stare decisis above, which at first may feel confusing. However, once you get to grips with this vocabulary and understand what they mean it will become second nature. Some of the most common terms you’ll encounter, along with those above, include:

Ratio Decidendi – Another Latin phrase, ratio decidendi is the reasoning behind the judge’s or court’s decision. It’s also legally binding on lower courts. to the reason for the judge or court decision.
Obiter Dicta – This refers to comments and thoughts shared by a judge on an aspect of the case. Often made in passing, these remarks are not vital to the actual decision. However, these comments can still be cited by others, especially when a law is unclear or still developing.
Binding Authority – A decision which sets a legal precedent that must be followed by lower courts in the same jurisdiction.
Persuasive Authority – This refers to a decision which influences an outcome, but it isn’t legally binding. For example, a court could look at a decision from another jurisdiction to help determine their own.
Distinguishing – A court can avoid following precedent by showing the facts of the current case are materially different from the earlier case. This can often be used for applying a law to a new situation.
Overruling – This occurs when a higher court decides a decision was wrong and overturns it. This changes the legal rule and alters the law for future cases.
Hierarchy of Courts – Knowing the structure of the court system is crucial to case law, as it helps ensure a systematic application of the law.